1. Field of the Invention
The present invention relates to EMI protective materials and more particularly, to an electromagnetic wave absorptive film that absorbs electromagnetic waves by means of destructive interference. The invention relates also to the fabrication of such an electromagnetic wave absorptive film.
2. Description of the Related Art
Following fast development of high technology, a variety of computers and digitalized communication apparatus and consumer electronic products have been disclosed and have appeared on the market. It is the market trend to make electronic products of relatively higher frequency. In consequence, consumers have a high chance of exposing the body to the harm of electromagnetic waves that may result in a high risk of leukaemia, encephalophyma, DNA destructive disease, and other diseases. According to studies, electromagnetic waves over 60 Hz become harmful to DNA in human cells. Some other foreign studies indicate influences of a cellular telephone to human brain such as temporary memory loss, lowering of the ability of behavior, etc. Because bad effects of electromagnetic waves have been continuously discovered, it has become the major research object in different fields to find electromagnetic wave protective materials.
Regular electromagnetic wave protective materials include electric field shielding materials and magnetic field shielding materials. Further, there are EMI (electromagnetic interference) protective materials prepared from mixture of metal fibers and other natural and synthetic fibers. Organic compound materials may be coated on a variety of materials such as metals, plastics, magnesium alloy, titanium alloy, aluminum alloy, wood, ceramics to change their surface characteristics, achieving EMI protective function.
However, conventional EMI protective materials commonly have a certain thickness that limits the application range. Nowadays, it is the market trend to develop cellular telephones and other electronic products having light, thin, short and small characteristics. When conventional EMI protective materials are used in small mobile electronic products, electromagnetic waves will still leak.
Therefore, it is desirable to provide an electromagnetic absorptive film that eliminates the aforesaid problems.